Xeon E5440: cache shared by core pairs

[LLevr]

Hi,

The Xeon 5440 is a quad-core with "2 x 6 MB" of cache (citing the specs). I've got clues that there is indeed 2 blocks of cache, each associated to 2 cores: my program launches equivalent threads, and when there are 3 of them, there is always one which runs faster; this doesn't happen with 4 threads.

So my question is: (where) can I find which core id's are paired with respect to cache? Is the naive assumption 0-1, 2-3 correct?

Thanks in advance.

[RGiff]

If you watch your CPU with windows Task Manager you will see the first core is always a little higher than the rest .

[RGiff]

I've got a X3380 that I replaced a QX9650 with and it spreads the work load better than the QX9650 ever did.